A New Technique for the Quantitative Estimation of Fibrinolysis using In Vivo [125I]Fibrinogen

Summary. A technique for the quantitative measurement of the fibrinolytic activity of blood is described, based on the rate of release of radioactivity in vitro from clotted blood obtained from patients previously receiving [125I]fibrinogen. The accuracy of the technique was assessed by comparison of the release of radioactivity with the appearance of fibrin degradation products, by observation of the effects of fibrinolytic inhibitors and by comparison of the initial fibrin content of the clot with the measurement of radioactivity released after total lysis. The measurement of fibrinolysis with this technique correlated well with the dilute blood clot lysis time in samples with a normal fibrinogen concentration, but the correlation was poor when the fibrinogen concentration was elevated. Since the measurement of fibrinolysis by this new technique is likely to be largely unaffected by the fibrinogen concentration, it is suggested that this technique is of particular value when the fibrinogen concentration is outside the normal range and, further, will allow significant comparison of fibrinolytic activity between blood samples of differing fibrinogen concentration.